Air conditioning system having reduced driving requirement

ABSTRACT

An air conditioning unit having a driven rotor with a plurality of vanes and defining a compressor portion and an expander portion, each having inlet and outlet ports, with a first heat exchanger connected between the compressor outlet port and the expander inlet port. A non-condensing gas such as air is fed into the compressor inlet port, compressed, cooled by the heat exchanger, and expanded back to substantially its initial pressure for discharge in the cold state at the expander outlet port, a non-condensing gas being defined as any gas which does not condense at the pressures and temperatures encountered in the unit. In accordance with the main feature of the present invention, means are provided for causing the non-condensing gas, as it enters the inlet port of the compressor, to be substantially saturated with a condensible additive fluid, having a high heat of vaporization and which condenses within the range of temperature achieved in the expander thereby to release heat of vaporization in the expander resulting in an increase in the work of expansion to reduce the net work required to drive the rotor. In one embodiment of the invention the system is open and air is used as gas, with water as the additive. In such embodiment the cold air is directly to the cooled space. In a second embodiment a second heat exchanger is connected between the expander outlet port and the compressor inlet port to form a closed loop sealed against escape of gas. When the system is closed, the gas and additive fluid may take many different forms, and a lubricant may be included to lubricate the vanes of the rotor.

United States Patent [191 Edwards 1 1 Oct. 21, 1975 AIR CONDITIONING SYSTEM HAVING REDUCED DRIVING REQUIREMENT [75] Inventor: Thomas C. Edwards, Casselberry,

Fla.

[73] Assignee: The Rovac Corporation, Maitland,

Fla.

[22] Filed: May 1, 1974 [21] Appl. No.: 465,841

Primary Examiner-William J. Wye Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

. [57] ABSTRACT An air conditioning unit having a driven rotor with a plurality of vanes and defining a compressor portion and an expander portion,'each having inlet and outlet ports, with a first heat exchanger connected between the compressor outlet port and the expander inlet port. A non-condensing gas such as air is fed into the compressor inlet port, compressed, cooled by the heat exchanger, and expanded back to substantially its initial pressure for discharge in the cold state at the expander outlet port, a non-condensing gas being defined as any gas which does not condense at the pressures and temperatures encountered in the unit. In accordance with the main feature of the present invention, means are provided for causing the noncondensing gas, as it enters the inlet port of the compressor, to be substantially saturated with a condensible additive fluid, having a high heat of vaporization and which condenses within the range of temperature achieved in the expander thereby to release heat of vaporization in the expander resulting in an increase in the work of expansion to reduce the net work required to drive the rotor. In one embodiment of the invention the system is open and air is used as gas, with water as the additive. In such embodiment the cold air is directly to the cooled space. In a second embodiment a second heat exchanger is connected between the expander outlet port and the compressor inlet port to form a closed loop sealed against escape of gas. When the system is closed, the gas and additive fluid may take many different forms, and a lubricant may be included to lubricate the vanes of the rotor.

15 Claims, 5 Drawing Figures US. Patent Oct. 21, 1975 Sheet30f3 3,913,351

AIR CONDITIONING SYSTEM HAVING REDUCED DRIVING REQUIREMENT It is an object of the present invention to provide an air conditioning unit of the compressorexpander type which, in addition to using a non-condensing gas, includes means for maintaining the gas substantially saturated with an additive fluid which; by condensing in the expansion portion of the cycle, increases the work of expansion and thus minimizes the driving power requirement. The reduction in the driving power requirement combined with the absorption of heat by the cold condensed (frozen) particles brings about a substantial increase in the coefficient of performance. It is a related object to provide an air conditioning unit having a compressor-expander in which a constantly replenished reservoir of additive fluid is provided at the compressor inlet for maintaining the gas, normally air, which enters the inlet substantially saturated. It is another object of the invention to provide an air conditioning unit of the above type in which the additive is replenished by condensate separated at the outlet of the expander for continuous re-cycling of the additive.

It is an object of the invention in one of its aspects to provide means for reducing the driving power requirements for a compressor-expander and which may be utilized with the system in open condition or in the form of a closed and sealed loop. Where the invention is utilized in the form of a closed and sealed loop the gas and additive may take many different forms without risk of polluting the atmosphere and may include a charge of lubricant to maintain the vanes of the compressor-expander in a constantly lubricated condition.

It is a further object of the present invention to provide an air conditioning system employing a compressor-expander in which the driving power requirements are reduced below that of a conventional system at minor cost and with a high degree of simplicity and reliability.

Other objects and advantages of the invention will become apparent upon reading the attached detailed description and upon reference to the drawings in which:

FIG. 1 is a diagram showing, in cross section, an air conditioning system employing the present invention and of the open type in which the gas used is air discharged in the cold state into a space.

FIG. 2 is a cross sectional view taken through the moisture separator looking along the line 22 in FIG. ll.

FIG. 3 is a diagram showing the increase in the work of expansion brought about by the present invention.

FIG. 4 shows forcible spraying in of moisture.

FIG. 5 is a cross sectional diagram showing the invention applied to a closed refrigeration system in which a gas, additive fluid, and lubricant are sealed from the atmosphere and continuously recirculated.

While the invention has been described in connection with certain preferred embodiments, it will be understood that I do not intend to be limited to the particular embodiments shown but intend, on the contrary, to cover the various alternative and equivalent forms of the invention included within the spirit and scope of the appended claims.

Turning now to FIG. 1, there is disclosed a compressor-expander having a frame 11 having formed therein a chamber of oval cross section defined by a wall 12. It will be understood that the chamber is enclosed, at its ends, with parallel end members (not shown) as described in my prior application Ser. No. 400,965 filed Sept. 26, 1973. Journaled in the end members is a rotor 20 having radially extending slidable vanes which may, for example, be ten in number and which have been designated 21-30 inclusive. The rotor has a shaft 32 which is journaled in bearings mounted in the respective end members of the shaft being connected to a source of driving power 33. The vanes are all pressed outwardly, in their respective slots, by an endless spring band 34 which engages the inner edges of each of them toform compartments 21'-30', respectively, which undergo changes in volume as the rotor rotates.

Assuming that the rotor turns in the direction shown by the arrows, the left half of the device acts as a compressor having an inlet port 41 and an outlet port 42, while the right-hand side acts as an expander having an inlet port 43 and an outlet port 44. Connected between the compressor outlet port 42 and the expander inlet port 43 is a first heat exchanger 45 which is provided to dissipate the heat of compression. Such heat exchanger is located outside of the compartment to be cooled, and the effectiveness of the heat exchange may be improved by using a motor-driven fan 46.

Coupled to the expander outlet port 44 for receiving the cold air from the unit 10 is an outlet assembly which performs a number of different functions, serving, primarily, as a heat exchanging device to subtract heat from the air in the controlled space. In this embodiment of the invention the heat exchange occurs as a result of mixing the air in the space with the air emanating from the expander, the mixed air being discharged through vents 51, 52. For this purpose, the outlet assembly has a mixing chamber 53 having an open or inlet end 54 and a fan or blower 55 of the squirrel cage type driven by a motor 56. Air from the blower passes through a connecting conduit into a plenum 57 for discharge through the ports 51, 52 previously referred to.

For introducing the cold air from the expander into the mixing chamber a porous moisture separator 60 is provided which may, for example, be formed of sin tered metal having a multiplicity of pores through which the cold air can escape while, nonetheless, retaining particles of ice or liquid moisture which may be entrained in the cold air from the expander. As set forth in greater detail in my copending application Ser. No. 420,712 filed Nov. 30, 1973 the porous element 60 is thermally coupled to the warmer, incoming air by means of longitudinally extending fins 61. The cold air is fed from the expander to the left hand end of the element 60 via an air line 62, the right-hand end of the element being enclosed. Assuming the air line 62 is insulated, or of short physical length, preferably both, and assuming that the cold air discharged from the expancler is below freezing, ice particles will be entrained in the air which is discharged into the element 60, but because of the constant warming of the element 60 by the incoming ambient air, the ice particles 'are melted and form condensate which runs to the bottom of the element as shown in FIG. 2.

In accordance with the present invention, means are provided for adding moisture to the air pulled into the compressor intake port 41, so that the inlet air becomes substantially saturated. As a result when the air subsequently expands on the expansion side of the device, accompanied by a sharp drop in both temperature and pressure, the moisture condenses out and is discharged at the expander outlet port 44 in the form of entrained ice particles, the condensation of the moisture from the saturated air causing the temperature on the expanded side to be greater than it would be without the added moisture. This, in turn, increases the work done by the expanding air so that the work required to rotate the rotor, per revolution, is reduced. As a result, less driving power is required from the drive 33 than would otherwise be required.

Further in accordance with the invention, the condensate from the porous moisture separation element 60, or at least a portion thereof, is recycled, being conducted to a reservoir or distributor, at the compressor inlet so that the reservoir is constantly replenished.

In the disclosed embodiment, the reservoirdistributor, indicated at 70, is in the form of a ring of sponge or other porous material having a large evaporative surface area and which is capable of forcibly distributing moisture to the incoming air stream. The condensate is conducted from the moisture removing element 60 to the distributor 70 via a condensate feed line 71. The ambient air which enters the compressor intake port 41 will normally have a certain percentage of moisture, so that all of the moisture which is separated out in the element 60 is not required for replenishment purposes. Accordingly, an overflow pipe 72 may be provided.

While the operation of the embodiment shown in FIGS. 1 and 2 will be apparent, it may be summarized briefly as follows: With the rotor driven by the drive 33 the air to be cooled is induced into the compressor inlet 41. As such air is drawn at high velocity past the reservoir 70, a high rate of evaporation takes place, causing the inlet air to be substantially saturated with moisture. This intentionally moisture-laden air is trapped in the spaces between adjacent vanes as for example in space 21. As the rotor rotates in the counterclockwise direction, the trapped air is compressed to a much smaller volume as indicated at 23' accompanied by a sharp rise in temperature. The high pressure, high temperature air, with its contained moisture, is then discharged through the compressor outlet 42 into the heat exchanger 45 where the air is cooled while being maintained at substantially constant pressure.

The cooled air passes into the expander inlet port 43, progressively expanding as it passes upwardly to the expander outlet port 44. Such expansion accomplishes two functions; it not only brings about a sharp drop in the temperature of the air for refrigeration purposes but the work of expansion tends to urge the rotor in the counterclockwise direction, thus assisting the driving means 33.

Because of the sharp drop in temperature and pressure, the intentional moisture in the air is condensed into the form of entrained ice particles or droplets. The mixture of the cold air and entrained moisture passes into the porous separator 60 where the air escapes and where the droplets of ice, deposited upon the inner walls, is melted by the heat of the incoming ambient air, with the water being separated out. The mixture of cold dry air and the incoming ambient air, passing into the plenum 57, is discharged in a comfortable. tempered state through the discharge vents 51, 52 into the controlled space.

The important feature of the present invention is thatthe intentionally added moisture, by reason of its condensation on the expander side, tends to raise the temperature of the expanding air to a level above that which would obtain if the moisture were absent. It can be quantitatively shown that this increase in temperature has the result of the substantially increasing work of expansion done upon the vanes, thereby minimizing the power requirements of the drive 33. Moreover, the presence of the added moisture, in the form of ice on the expansion side, increases the heat capacity of the air-water mix which passes through the unit at each revolution by making greater use of the latent heat of the ice particles in addition to the sensible heat of the water particles and the air itself, thereby to achieve a greater cooling effect per revolution. The result of the two effects, in combination, is to bring about a substantial improvement in the coefficient of performance of a practical system, that is, the ratio between the cooling capacity per rotative cycle to the work which is done by the external driving means during such cycle. By reason of the improvement, that is, the intentional addition of water at the compressor inlet port, a coefficient of performance may be achieved on the order of 3 or 4 to 1, whereas in a conventional freon system it is generally considered satisfactory to achieve a coefficient of performance on the order of 2.

In order to obtain a quantitative assessment of the positive effect of moisture on the systems performanee, let it be assumed that the expansion process, wet or dry air, can be described by the polytropic. (i.e.: PV" Const) In FIG. 3 the expansion process is indicated by the P-V trace with n the parameter. The term ri indicates dry air polytropic index (which is on the order of 1.35 for real processes of the nature considered here). The term n indicates the. wet air polytropic index and this value has been shown to be about 1.25. (The manner in which this value of n is derived is explained subsequently.)

As noted from FIG. 3, the volume, V that the air must-expand to in order to reach ambient pressure, is greater than that required for dry air (V The effect of this is seen to be a larger area of work recovery (expansion) which is f pdV where V,- indicates the initial volume and V, indicates the final volume of expansion. In order to quantify this -Continued .Wmr, 116.2 in lbf Next, calculate the same quantity for wet air expansion (n 1.25):

The total work put into the air cycle machine is the difference between the compression work and expansion work:

WT rump For dry air we obtain:

For wet air the result is:

The ratio of work input, wet-to-dry is:

rnmp This indicates that an increase in performance of 11 percent can be expected due to the increased work of expansion of wet air alone. There is, however, yet another very important aspect of the wet-air (two-phase) air cycle preocess: The change of phase effected during expansion involves and increase in the total cooling capacity. The total cooling capacity is the sum of the latent and sensible energy. The sensible energy, made up of the actual temperature difference across the inlet and outlet of the circulator, is somewhat reduced due to the moistureJ-iowever, the latent heat is quite large so that the total sum is significantly larger than that of dry air alone. Using some additional data, we can quantify this difference in cooling capacity.

Q1 Qumm QSenxlhlP where Qsrmvible "I CP 1,7 1,111) and QLalnll MHO n o The sensible heat can easily be calculated from data a]- ready given and produced.

For dry air:

For wet air:

Qm)1m= 0.00817 BTU/segment The latent cooling content can be calculated from a knowledge of the inlet humidity ratio and the latent heat of fusion and freezing. Under average conditions, the inlet humidity ratio is on the order of 0.015 lbm water per pound of dry air. The total heat of fusion is on the order of l BTU/lbm. Therefore, we can estimate the latent heat per segment as:

Q fl 0.00817 0.0055 0.01367 BTU/segment It is to be noted that the heat absorbed by the melting ice from the intentionally added moisture adds substantially to the thermal capacity. It can be seen fromm the above calculation that the cooling capacity is increased a total of somewhat more than 30 percent. This means that the coefficient of performance (cooling cap/work in) has increased more than 45 percent. This is seen to be an important increase in efficiency and is therefore a significant consideration in comparison with prior systems.

Not only does the intentional addition of water at the compressor inlet bring about a higher coefficient of performance of the system as a whole, but it is one of the features of the illustrated system that this improvement is brought about at little or no increase in expense. Moreover, no additional care or maintenance is required since the condensate feeds constantly through line 71 at a slow rate to replenish the moisture lost at the distributor 70, and with any excess moisture in the separator 60 draining away harmlessly through the overflow 72.

Note that in the system disclosed in FIGS. 1 and 2 the tempered air which is discharged into the controlled space via the vents 51, 52 is of relatively low humidity, comfortably dry, notwithstanding the fact that moisture has been intentionally added to the air at the compressor inlet. However, the invention is not limited to the production ofa cool mix of relatively dry air but the invention is applicable, as well, to controlled spaces having a high humidity requirement. The desired level of moisture may be added to the air stream by forming a controllable vent or bypass in the side of the moisture separator element 60. It is, indeed, one of the features of the present system that it may be used for intentionally loading the air in a cooled space with moisture as for example in the transport and storage of perishable fruits and vegetables. This can be done in the system of FIG. I by simply omitting the porous separator so that the ice and condensed water particles, instead of being intercepted, are simply blown by the cold air into the incoming stream of ambient air from the cooled space which serves to melt the ice particles. The proportion of ambient air to cold air may be predetermined by selecting the rating and speed of the blower or fan assembly 55, 56. Moreover, fresh outside air may be incorporated by using a proportioning valve at inlet 54. If desired the cooled air and entrained ice may be discharged into the refrigerated space directly from the discharge outlet 44 without any pre-mixing with ambient air. When the moisture is not intercepted, and the water is not recycled, the feed line 71 may be supplied from any convenient source of liquid water such as a storage tank.

The invention has been described above in connection with an open system in which the gas which is processed by the compressor-expander is air and in which the liquid additive is water. However, the invention in certain of its aspects is not limited thereto and is applicable, with certain additional advantages, to a closed system in which a second heat exchanger, similar to the first heat exchanger, is directly interconnected between the expander outlet port and the com pressor inlet as shown, for example, in FIG. 5. In this figure corresponding reference numerals have been used, where applicable, with addition of subscript a. The two systems, open and closed, are similar in most respects. Indeed, the main difference is that the system of FIG. being closed, may be permanently charged with a fluid additive so that there is no necessity for feeding make-up in liquid form. Instead, the reservoirdistributor 70a consists of two parts, a ring of sponge or other porous material in capillary engagement with a pool of additive 70b.

The similarities in operation between the two versions is best brought out by assuming that the system is charged with a mixture of air and water prior to being sealed, with excess water in the pool or reservoir 70b wetting the sponge 70a. Thus as the rotor a rotates being driven by the drive 33a, in the direction shown by the arrows, air is drawn into the inlet 41a past the water-saturated sponge 70a to insure that the air passing into the compressor is saturated (or nearly so) with moisture. The air-water mix trapped between adjacent vanes is progressively compressed and passes through the outlet 42a into the first heat exchanger 45a where the mix is cooled to near ambient temperature, while maintaining the pressure near constant at a relatively high level. Subsequently, as the air flows into the inlet port 43a on the expander side and is expanded in the compartments defined by the vanes, a temperature drop occurs accompanied by condensation of the moisture in the form of ice particles or droplets. This brings about the same benefit as was discussed in connection with the earlier embodiment, that is, greater recovery of the work of expansion resulting in reduced drive power requirements. The air stream with its entrained ice passes into the second heat exchanger 50a which is located in the controlled space and which is coupled to the space by the illustrated fins and forced air fan 55a. Internal baffles 61a may be used in the heat exchanger with drain holes 61b, to intercept the ice particles or cold droplets to facilitate heat transfer. By reason of the heat exchange, the space is cooled, accompanied by melting of the ice and an increase in temperature of the enclosed air, with the heat of fusion of the ice and sensible heat of the cold droplets adding to the thermal capacity of the unit, just as previously mentioned.

The moisture, or condensate, resulting from the melting ice is forced along the inner surfaces of the second heat exchanger 50a, running down the walls of the con nection 71a where the moisture is collected by the sponge a and re-distributed to the air stream entering the compressor, thereby completing an operating cycle.

Since the motor 56a which drives the fan consumes an amount of power which is comparable to the motor 56 which drives the blower in the earlier embodiment, it will be understood that from the standpoint of power requirements, the two systems are much the same. The main advantage of the second or closed system is that it permits use of a wider variety of gases and additives since neither the gas nor additive is discharged into the open air and, moreover, the system may be charged with lubricant soluble in, or miscible in, the additive to provide constant lubrication of the vanes 21a-30a. For example, the same emulsified lubricant may be used as in machine tool practice. Thus any gas may be used which is non-condensing at the temperatures and pressures encountered during the course of the cycle, and any additive may be used having a high heat of vaporization (preferably approaching that of water) upon change of state during the course of a cycle. A high heat of fusion is also desirable. If air is employed as the gas, the additive may, for example, be in the form of alcohol or a hydrocarbon such as benzine, both of which are capable of undergoing a change in state in practically encountered temperatures and pressures. Instead of using air, carbon dioxide may be employed or, indeed, almost any other gas which is stable, noncorrosive, and non-condensing at the encountered temperatures and pressures. Any lubricant may be used which is soluble or miscible with the additive, for example, common lubricating oil. Or, if desired, an additive may be employed which has inherent lubricating properties, in addition to its condensing properties.

It will be apparent to one skilled in the art that practice of the invention is not limited to use of a common or existing substance as an additive. Much work has already been done on the synthesizing of new fluorohydrocarbon compounds for the purpose of achieving predetermined change of state characteristics. In the case of the present device, used in a closed system, it may be desirable, by way of example, to have an'additive which evaporates within the range of to 200F. over a pressure range of 14 to 50 pounds per square inch and which will condense in the range of 100 to 0F. within the same pressure range. It is, of course, preferable to be able to choose an existing commercial substance having these'properties but, as an alternative, the additive may be synthesized, either as a single substance or as a combination of two substances, each individually suited to function either during compression or expansion. The synthesizing procedure is, of course, outside of the scope of the present invention.

In the above discussion a sponge or other porous element 70, 70a has been utilized for distributing the additive to the incoming air stream. Because of the brief contact between the distributor and the passing air, or gas, complete saturation is not assured, and the term substantially saturated" has been used thus far to refer to either a condition of full saturation or a condition in which the amount of additive taken up by the gas (degree of relative humidity in the case of water) is less than saturation but greater than that which would occur absent the intentional addition.

Indeed, a carburetor of automotive design may be interposed in the air stream at the compressor inlet port, modified only to the extent of having a pressure drop and nozzle size suited to the viscosity characteristics of the additive being used. As an alternative, a small nozzle 70b, FIG. 4, may be introduced into the air stream at the compressor inlet port 41, with the pressure being augmented by a pump P. If desired, an atomizer A, positioned slightly downstream from the nozzle, may be provided for acting upon the relatively gross droplets and for breaking them up into smaller size. The atomizer may, for example, be in the form of a turbine wheel either separately or self-driven or in the form of a piezoelectric crystal vibrated at sonic or ultrasonic frequency.

The term ambient is a general one including air in the space, outside air, or a mixture of the two. The term vanes as used herein will be understood to broadly include any partition means defining chambers which are progressively compressed in size, and enlarged, for the compressor and expander functions. The term second heat exchanger as used herein refers to any means, located at the outlet port of the expander, which brings about a heat transfer between the air in the space to be cooled and the air which flows from the outlet port. In the case of the closed system this heat exchanger is, of course, that which is indicated at 50a. In the case of the open system the mixing chamber 53 and the porous moisture separator 60 together with the means for inducing flow of air therethrough, bring about a heat exchanging function and thus satisfy the term heat exchanger. Any heat exchange means whatsoever suffices.

Also while it is preferred to use a compressorexpander unit which employs a rotor cooperating with a stator of oval cross section to form compressor and expander portions, it is understood that the invention is not necessarily limited thereto and that the invention may be practiced, if desired, employing a separate vane type compressor and a vane type expander, each with appropriate inlet and outlet ports, and arranged axially end to end. Indeed, any device having a common shaft with means for first compressing and then expanding a gas may be employed in making use of the invention.

The term air conditioning" will be understood to be synonomous with refrigeration. Nevertheless, while the above described system is intended primarily for cooling purposes, it will be understood that it may be also employed as a heat pump by mounting the first heat exchanger 45a in the controlled space and a second heat exchanger 50a in the outside ambient; thus the term air conditioning is intended to cover heating as well as cooling.

What I claim is:

1. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger coupled to the expander outlet port, the heat exchangers being isolated from one another for communication with separate compartments, means for conducting inlet air to the compressor inlet port so that upon driving of the rotor means the air (I) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and a reservoir of water at the compressor inlet port adjacent the path of air flow to insure that the air which flows into the compressor is substantially saturated with water va por, the air being sufficiently cooled in the expander as to cause condensation of the vapor with release of its heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor, and with the condensed vapor serving to absorb heat in the second heat exchanger thereby to augment the cooling effect of the air therein.

2. The combination as claimed in claim 1 in which the second heat exchanger has means for intercepting the condensed water vapor in the form of droplets or ice particles to utilize the cooling effect thereof while permitting passage of the air.

3. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger connected to the expander outlet port, the heat exchangers being isolated from one another for communication with separate compartments, means for conducting to the compressor inlet port a gas which is non-condensing at the temperatures and pressures encountered in the unit so that upon driving of the rotor means the gas (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and an additive fluid in the gas, the additive being a fluid having a high heat of vaporization which is in substantially saturated vapor form at the compressor inlet port and which condenses within the range of temperature and pressure achieved in the expander with release of heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor and with the condensed vapor serving to absorb heat in the second heat exchanger thereby to augment the cooling effect of the air therein.

4. The combination as claimed in claim 3 in which a reservoir-distributor for additive in liquid form is provided in association with the compressor inlet port adjacent the path of the flow of gas to insure that'the gas is maintained substantially saturated with the additive.

5. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger connected to the expander outlet port, the heat exchangers being isolated from one another for communication with separate compartments, means for conducting to the compressor inlet port a gas which is non-condensing at the temperatures and pressures encountered in the unit so that upon driving of the rotor means the gas l is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and an additive fluid in the gas, the additive being a fluid having a high heat of vaporization which is in substantially saturated vapor form at the compressor inlet port and which condenses within the range of temperature and pressure achieved in the expander with release of its heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor and with the condensed additive serving to absorb heat in the second heat exchanger thereby to augment the cooling effect of the gas, and means for coupling the second heat exchanger to the compressor inlet port so that the gas and the additive in the gas are conserved for continuous recirculation.

6. The combination as claimed in claim 5 in which a baffle is provided in the second heat exchanger for in tercepting the condensed additive to insure utilization of the cooling effect thereof.

7. The combination as claimed in claim 5 in which the additive exists in the gaseous, liquid and solid states within the range of temperatures and pressures encountered in the unit, and in which means are provided in association with the second heat exchanger for intercepting additive in the solid and liquid states for absorption of latent and sensible heat, and means for conducting additive in the liquid state from the intercepting means to the compressor inlet port for redistribution to the gas flowing therethrough to substantially saturate the same. i

8. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger connected to the expander outlet port, the heat exchanger being separated from one another for communication with separate compartments, means for conducting to the compressor inlet port a gas which is non-condensing at the temperature and pressures encountered in the unit so that upon driving of the rotor means the gas (1 is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and an additive fluid in the gas, the additive being a fluid having a high heat of vaporization which is in substantially saturated vapor form at the compressor inlet port and which condenses within the range of temperature and pressure achieved in the expander with release of heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor means, a porous distributor at the compressor inlet port, and means for conducting additive fluid thereto in the liquid state, the porous distributor being positioned in the stream of gas entering the inlet port for forcible evaporation of the additive fluid into vapor state.

9. An air conditioning system for cooling an enclosed space, comprising in combination an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the-rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, mounted therein having a plurality of vanes, a heat exchanger connected between the compressor outlet port and the expander inlet port, means for conducting air from the space to the compressor inlet port so that upon driving of the rotor the air (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the heat exchanger, and (3) is positively expanded and lowered in temperature in the expander, means including a distributor at the compressor inlet port for distributing water to the inlet air at the compressor inlet port to increase the moisture therein to a point of substantial saturation, means interposed at the expander outlet port for filtering out the resulting particles of moisture to produce cold dry air, and means for mixing the cold dry air with the air in the space for lowering the temperature of the latter.

10. The combination as claimed in claim 9 including an auxiliary fan for forcibly mixing the air in the space with the cold air in predetermined proportion.

11. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a heat exchanger connected between the compressor outlet port and the expander inlet port, means defining an air mixing chamber connected to the expander outlet port, the heat exchanger and mixing chamber being isolated from one another for communication with separate compartments, means for. conducting inlet air to the compressor inlet port, the de gree of compression and expansion being sufficiently great so that upon driving of the rotor the air (1 is positively compressed and elevated in temperature in the compressor, (2) releases heat in the heat exchanger, (3) is positively expanded and lowered below freezing temperature on the expander, and (4) discharges into the mixing chamber, the mixing chamber having a porous filter for catching entrained ice particles resulting in a stream of dry cold air, said mixing chamber also having means for including the flow of relatively warm ambient air adjacent the filter for melting of the ice particles to form condensate and for mixing with the dry cold air to temper the same, and means for conducting at least part of the condensate to the compressor inlet port to maintain the inlet air substantially saturated with moisture.

12. The combination as claimed in claim 5 in which the additive includes a lubricant soluble or miscible therein for lubricating the vanes.

13. The combination as claimed in claim 12 in which the additive is water and in which the lubricant is a petroleum product emulsified therein.

14. An air conditioning system comprising, in combination, a compressor-expander coupled together having a compressor and an expander of the positive displacement type each having an inlet port and an outlet port and with a common drive shaft, a heat exchanger connected between the compressor outlet port and the expander inlet port, means for conducting gas to the compressor inlet port so that upon rotation of the drive shaft the gas (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the heat exchanger, and (3) is positively expanded and lowered in temperature on the expander, an additive in the gas in the form of a fluid having a high heat of vaporization, the gas being of a type incapable of condensing and the additive fluid being of a type capable of condensing within the range of temperature and pressure existing in the unit, and means for distributing additional additive fluid to the gas entering the compressor inlet port.

15. The combination as claimed in claim 14 in which the additive fluid is so chosen that it exists in three states within the ranges of temperature and pressure existing in the unit. 

1. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger coupled to the expander outlet port, the heat exchangers being isolated from one another for communication with separate compartments, means for conducting inlet air to the compressor inlet port so that upon driving of the rotor means the air (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and a reservoir of water at the compressor inlet port adjacent the path of air flow to insure that the air which flows into the compressor is substantially saturated with water vapor, the air being sufficiently cooled in the expander as to cause condensation of the vapor with release of its heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor, and with the condensed vapor serving to absorb heat in the second heat exchanger thereby to augment the cooling effect of the air therein.
 2. The combination as claimed in claim 1 in which the second heat exchanger has means for intercepting the condensed water vapor in the form of droplets or ice particles to utilize the cooling effect thereof while permitting passage of the air.
 3. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger connected to the expander outlet port, the heat exchangers being isolated from one another for communication with separate compartments, means for conducting to the compressor inlet port a gas which is non-condensing at the temperatures and pressures encountered in the unit so that upon driving of the rotor means the gas (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and an additive fluid in the gas, the additive being a fluid having a high heat of vaporization which is in substantially saturated vapor form at the compressor inlet port and which condenses within the range of temperature and pressure achieved in the expander with release of heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor and with the condensed vapor serving to absorb heat in the second heat exchanger thereby to augment the cooling effect of the air therein.
 4. The combination as claimed in claim 3 in which a reservoir-distributor for additive in liquid form is provided in association with the compressor inlet port adjacent the path of the flow of gas to insure that the gas is maintained substantially saturated with the additive.
 5. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger connected to the expander outlet port, the heat exchangers being isolated from one another for communication with separate compartments, means for conducting to the compressor inlet port a gas which is non-condensing at the temperatures and pressures encountered in the unit so that upon driving of the rotor means the gas (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and an additive fluid in the gas, the additive being a fluid having a high heat of vaporization which is in substantially saturated vapor form at the compressor inlet port and which condenses within the range of temperature and pressure achieved in the expander with release of its heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor and with the condensed additive serving to absorb heat in the second heat exchanger thereby to augment the cooling effect of the gas, and means for coupling the second heat exchanger to the compressor inlet port so that the gas and the additive in the gas are conserved for continuous recirculation.
 6. The combination as claimed in claim 5 in which a baffle is provided in the second heat exchanger for intercepting the condensed additive to insure utilization of the cooling effect thereof.
 7. The combination as claimed in claim 5 in which the additive exists in the gaseous, liquid and solid states within the range of temperatures and pressures encountered in the unit, and in which means are provided in association with the second heat exchanger for intercepting additive in the solid and liquid states for absorption of latent and sensible heat, and means for conducting additive in the liquid state from the intercepting means to the compressor inlet port for redistribution to the gas flowing therethrough to substantially saturate the same.
 8. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a first heat exchanger connected between the compressor outlet port and the expander inlet port, a second heat exchanger connected to the expander outlet port, the heat exchanger being separated from one another for communication with separate compartments, means for conducting to the compressor inlet port a gas which is non-condensing at the temperature and pressures encountered in the unit so that upon driving of the rotor means the gas (1) is positively compressed and elevated in temperature in the compressor, (2) rEleases heat in the first heat exchanger, (3) is positively expanded and lowered in temperature in the expander, and (4) absorbs heat in the second heat exchanger, and an additive fluid in the gas, the additive being a fluid having a high heat of vaporization which is in substantially saturated vapor form at the compressor inlet port and which condenses within the range of temperature and pressure achieved in the expander with release of heat of vaporization, resulting in an increase in the work of expansion and thereby reducing the net work required to drive the rotor means, a porous distributor at the compressor inlet port, and means for conducting additive fluid thereto in the liquid state, the porous distributor being positioned in the stream of gas entering the inlet port for forcible evaporation of the additive fluid into vapor state.
 9. An air conditioning system for cooling an enclosed space, comprising in combination an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a heat exchanger connected between the compressor outlet port and the expander inlet port, means for conducting air from the space to the compressor inlet port so that upon driving of the rotor the air (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the heat exchanger, and (3) is positively expanded and lowered in temperature in the expander, means including a distributor at the compressor inlet port for distributing water to the inlet air at the compressor inlet port to increase the moisture therein to a point of substantial saturation, means interposed at the expander outlet port for filtering out the resulting particles of moisture to produce cold dry air, and means for mixing the cold dry air with the air in the space for lowering the temperature of the latter.
 10. The combination as claimed in claim 9 including an auxiliary fan for forcibly mixing the air in the space with the cold air in predetermined proportion.
 11. In an air conditioning system, an air conditioning unit including a compressor and expander having rotor means driven by a common shaft, the rotor means having vanes defining enclosed compartments which become smaller and larger as the shaft rotates, the compressor and expander each having an inlet port and an outlet port, a heat exchanger connected between the compressor outlet port and the expander inlet port, means defining an air mixing chamber connected to the expander outlet port, the heat exchanger and mixing chamber being isolated from one another for communication with separate compartments, means for conducting inlet air to the compressor inlet port, the degree of compression and expansion being sufficiently great so that upon driving of the rotor the air (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the heat exchanger, (3) is positively expanded and lowered below freezing temperature on the expander, and (4) discharges into the mixing chamber, the mixing chamber having a porous filter for catching entrained ice particles resulting in a stream of dry cold air, said mixing chamber also having means for including the flow of relatively warm ambient air adjacent the filter for melting of the ice particles to form condensate and for mixing with the dry cold air to temper the same, and means for conducting at least part of the condensate to the compressor inlet port to maintain the inlet air substantially saturated with moisture.
 12. The combination as claimed in claim 5 in which the additive includes a lubricant soluble or miscible therein for lubricating the vanes.
 13. The combination as claimed in claim 12 in which the additive is water and in which the lubricant is a petrOleum product emulsified therein.
 14. An air conditioning system comprising, in combination, a compressor-expander coupled together having a compressor and an expander of the positive displacement type each having an inlet port and an outlet port and with a common drive shaft, a heat exchanger connected between the compressor outlet port and the expander inlet port, means for conducting gas to the compressor inlet port so that upon rotation of the drive shaft the gas (1) is positively compressed and elevated in temperature in the compressor, (2) releases heat in the heat exchanger, and (3) is positively expanded and lowered in temperature on the expander, an additive in the gas in the form of a fluid having a high heat of vaporization, the gas being of a type incapable of condensing and the additive fluid being of a type capable of condensing within the range of temperature and pressure existing in the unit, and means for distributing additional additive fluid to the gas entering the compressor inlet port.
 15. The combination as claimed in claim 14 in which the additive fluid is so chosen that it exists in three states within the ranges of temperature and pressure existing in the unit. 